1. Field of the Invention
The present invention pertains to a fuel vapor filter, and more particularly, pertains to a carbon-filled fuel vapor filter canister.
2. Description of the Prior Art
Gasoline Emission Control--A principal application of activated carbon is in the capture of gasoline vapors that escape from vents in automotive fuel systems. Under EPA regulations, all U.S. motor vehicles produced since the early 1970s have been equipped with evaporative emission control systems. Most other auto producing countries now have similar controls. Fuel vapors vented when the fuel tank or carburetor is heated are captured in a canister containing 0.5 to 2 L of activated carbon. Regeneration of the carbon is then accomplished by using intake manifold vacuum to draw air through the canister. The air carries desorbed vapor into the engine where it is burned during normal operation. Activated carbon systems have also been proposed for capturing vapors emitted during vehicle refueling. Activated carbon is used at many gasoline terminals to capture vapor displaced when tank trucks are filled, after the car has been turned off after having run, sitting in hot weather, and at the gas station. Typically, the adsorption vessels contain around 15 m.sup.3 of activated carbon and are regenerated by application of a vacuum. The vapor that is pumped off is recovered in an absorber by contact with liquid gasoline. Similar equipment is used in the transfer of fuel from barges. The type of carbon pore structure required for these applications is substantially different from that used in solvent recovery. Because the regeneration conditions are very mild, only the weaker adsorption forces can be overcome, and therefore, the most effective pores are in the mesopore size range. A large adsorption capacity in these pores is possible because vapor concentrations are high, typically 10-60%.
Prior art fuel vapor filters have included loose carbon granules in a housing. The cost to manufacture these types of fuel vapor filters as either original equipment, or after-market equipment is expensive. Further, the granules can sink and settle, and loose their efficiency over time. Furthermore, prior art fuel vapor filters have numerous parts which require manufacture and later assembly.
FIG. 1 illustrates a representative prior art fuel vapor filter with many parts, all of which are eliminated by the present invention.
The process used to manufacture these canisters is expensive and dirty. Most importantly the current technology for current loose carbon granule type canisters requires many parts. These parts are eliminated with the herein described invented carbon block technology. In addition, due to settling problems of granular carbon fuel vapor filters in the prior art, the canisters are not filled to capacity.
Prior art canister filters that use loose granules can be converted to block technology and will hold more carbon, thus increasing performance capacity. Many parts that are in the prior art loose type canisters will be eliminated. These include bottom retainer screen and foam pad, pressure retaining strip and lock nut and foam pad and filter paper. Channelling in the present invention is eliminated by using a block of bonded carbon pellets for the present invention. As air will take the course of least resistance a passageway could eventually develop, whereby the air will be taking a path not coming into contact with any carbon, which will then render the prior art canister virtually useless.
The present invention provides a fuel vapor filter which includes carbon pellets bound together with a polymer to prevent settling or compacting, and also addresses the shortcomings of the prior art devices by eliminating prior art parts, and eliminating channeling and also providing a cleaner manufacturing process.